UC San Diego

Reactions in the mineral surface/reservoir fluid interface control geochemical processes such as the dissolution and growth of minerals. In this dissertation we present properties of hematite bulk, AIMD simulation of structures and reactions (Fe2+ absorption) in the hematite–water interfaces region with intension of interpreting the structure of the reactive interface region, the dynamics of the water, solute molecules and atoms in this region and the electronic structure associated with hydrogen and covalent bond formations.

We also study symmetry breaking in the mean field solutions to the 2 electron hydrogen molecule within Kohn Sham (KS) local spin density function theory with Dirac exchange (the XLDA model). This simplified model shows behavior related to that of the (KS) spin density functional theory (SDFT) predictions in condensed and molecular systems. The Kohn Sham solutions to the constrained SDFT variation problem undergo spontaneous symmetry breaking as the relative strength of the non-convex exchange term increases. This results in the change of the molecular ground state from a paramagnetic state to an antiferromagnetic ground states and a stationary symmetric delocalized 1st excited state. We further characterize the limiting behavior of the minimizer when the strength of the exchange term goes to infinity. The stability of the various solution classes is demonstrated by Hessian analysis. Finite element numerical results provide support for the formal conjectures.

In Chapter 1 experimental and theoretical backgrounds and progress are introduced. In Chapter 2 computational methods including first principle methods and AIMD are briefly introduced. %In Chapter 3 the properties of hematite bulk are calculated and analyzed.

In Chapter 3 simulations of surface and aqueous fluid interfaces of hematite (001) and (012) are carried out. Projected density of states for interfacial atoms, water adsorption process on surface, hydrogen bond analysis, electron density profiles and etc are investigated. In Chapter 4 symmetry breaking in density functional theory due to Dirac exchange for a Hydrogen molecule is studied. In Chapter 5 Dynamic Mean Field Theory method and applications are presented. In Chapter 6 summary and future work are discussed.